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Capacitive Power Supply Direction

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JimB

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The quick answer is yes it is ok.

Just be aware of which bits are live and which are neutral, make sure that you or anyone else does not touch it when it is energised and it will be fine.
I am sure that you are experienced enough to know that already.

JimB
 

ronsimpson

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Several comments.
Line and Neutral wires can be exchanged with out a problem.
Another internet schematic that will not work! R2 is in the wrong place!
R1, R3 must be a high voltage resistor or several in series.
D1, D2 do not need to be the high voltage 1N4007 but could be the low voltage 1N4001.
R3 is to find "zero crossing" information BUT I think this same information can be found at node C1,D1,
D2, (but at a much lower voltage) About 5 volts so a 10k resistor will also work. I have not tried it but I could if you want.
------------------------
Just tried it and you get a 5V signal where the "edges" happen at the peaks of the line voltage. (not at the "zero crossing")



upload_2017-9-24_12-10-57.jpeg
 

ronsimpson

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I moved R2 to get it out of the high current path of X1 60W.
There are several parts that don't need to be there. Do you want a simple version?
upload_2017-9-24_12-14-11.png
 

Suraj143

Active Member
hi ron thanks for the circuits.you are correct.I placed the R2 @ wrong place.

regarding the low voltage zero cross detector.can it give signals on zero cross?I need to detect zero cross, not the peak of the waveform.
 

Suraj143

Active Member
Hi ron

I'm bit of scared about the last circuit.because the zenner is mostly busy on both AC cycles.I like to stick with the design on your post number 4.But the zerocross I moved to hot wire.

I need to consider the circuit more robust.I added a MOV 275V to parallel live and neutral.Does it give a circuit protection without a fuse?I have a limited pcb space.

Regarding the hot wire sensing zerocross,

Will the lightneing strike pass through easily from this zerocross resistor?
 

Suraj143

Active Member
Hi I have a simulation problem.The current this circuit will producing is very low.Or my simulation is wrong.Because I need to find a commonly available triac with adequate gate current.
 

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MikeMl

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What is the current through D2?
 

Suraj143

Active Member
Hi actually I don't know the current.Attached the LTspice sim.I'm going to use BTB04 Triac. From this supply my load will be PIC, BTB04 triac & a RED LED.
 

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ronsimpson

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Supply is about 9mA.
The BTB04 is no longer in production at ST. Needs 10mA in Q1/Q3/Q4. I am not good with triacs! What about Q2?
Does the red LED have to be on while the triac is on?
>If the triac needs 10mA and the LED needs 10mA but they are exclusive to each other, then there is a chance.
>Is the LED switched on/off? or does it stay on all the time? (all the time .... I have a way that does not load the supply)
> Do you drive the gate of the triac 100% of the time. The 220uF cap (I used 470) can supply 40mA for 1/4 of the time.
 

Suraj143

Active Member
Supply is about 9mA.
The BTB04 is no longer in production at ST. Needs 10mA in Q1/Q3/Q4. I am not good with triacs! What about Q2?
Does the red LED have to be on while the triac is on?
>If the triac needs 10mA and the LED needs 10mA but they are exclusive to each other, then there is a chance.
>Is the LED switched on/off? or does it stay on all the time? (all the time .... I have a way that does not load the supply)
> Do you drive the gate of the triac 100% of the time. The 220uF cap (I used 470) can supply 40mA for 1/4 of the time.
Good to know about BTB04 is no longer in production, so I can shift to a new one (but I searched in local market,it is very hard to find sensitive gate triacs.I only found BTB04 & BT139-600E).

Regarding the LED, this LED is blinking.It never continously ON :)

The triac is turn ON for a time period of 15 mins.While the triac is ON the LED will be blinking.

Planned to drive the gate of the triac for 15 mins.

There is no Q2 in the above diagrams :)
 

ronsimpson

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There is no Q2 in the above diagrams
Q1,2,3,4 is quadrants. Has to do with gate + or - and load being + or -.

I can get the LED to light with no draw from the 5V power.
OR
I can pass the gate current through the LED so they are both on. (no blink)
 

ronsimpson

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Next idea:
Full wave will get you 2x more current! But you will not be able to drive the triac.
-----------------------------
MOC3023 isolutes the mico from the triac. (so full wave will work) and the MOC3023 needs only 5mA. MOC3022 = 10mA, MOC3021 = 20mA There are many triac opto isolators. This is one I have. You can find better parts.
Point is: full wave is 2 more diodes. Less ripple on the +5 supply. Possible smaller high voltage capacitor. (add two diodes and cap 1/2 size) Now the gate current on the BIG triac does not matter.
upload_2017-10-3_10-41-15.png
 

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Suraj143

Active Member
Hi,

I changed the design as suggested.Used a 5mA opto-isolator.Zero Cross also taken from the low voltage side.When the Live & Neutral swap, the Zero Cross will be detect from Neutral side.I hope it won't give a problem...!!
 

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ronsimpson

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Have you looked at the MOC3063.
It includes a zero crossing detector.
You can turn on the LED at any time but the triac will delay until the next zero crossing.
Are you doing dimming?
 

ronsimpson

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the Zero Cross will be detect from Neutral side
The green trace is what the micro will see for "zero detector". This is really peak detect. With a little software you can find the "zero" time.
Blue is the supply voltage.
Red is the line voltage/50, not referenced to anything.
upload_2017-10-5_20-5-30.png
 

Suraj143

Active Member
Hi,

I made the full wave circuit.The problem is when using 5.1V zenner diodes the final output I got only 4.5V. I have a preset 10K which is measuring A to D value to determine the timing of this timer circuit.When the supply voltage drops below 5V the internal analog reference is varying :( I changed the zenners to 5.6V. Is it ok?
 

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ronsimpson

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I have a preset 10K which is measuring A to D value to determine the timing of this timer circuit.When the supply voltage drops below 5V the internal analog reference is varying :(
More informaton:
Which micro?
What is the "internal analog ref." voltage?
 

Suraj143

Active Member
Hi
I use PIC12F675.Internal referance is 5V.I dont need much accuracy.I just need to scale the full scale A/D to 10 values.
 
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